1. Field of the Invention
The present invention relates to the mining industry, construction and transport, and more particularly it relates to shield units.
The present invention can find most efficient application in mining, tunnelling, coal chuting, as well as in driving workings for switchgears and power plants.
2. Description of the Related Art
There is known a shield unit (SU, A, 1229354), comprising a cylindrical shell made up of two sections (head section and tail section) arranged in succession one after the other which are connected by means of a traversing mechanism, the head section being provided with a cutting tool, its outer portion having a helical surface, and the tail section being outfitted with a device preventing its rotation in rock. The tail section of the shield unit consists of two parts, the first one serving as a support in case the head section turns or moves and the second one serving as a support in case the first part of the tail section turns or moves. A helical surface is provided on the outer portion of the tail section. The traversing mechanism includes two groups of double-action hydraulic jacks. The first group of hydraulic jacks is used for turning and axial movement of the head section relative to the tail section. The second group of hydraulic jacks is used for turning and axial movement of the first part of the tail section relative to its second part. Each hydraulic jack is in fact a cylinder with a piston and a rod. The cylinders of hydraulic jacks of the first group are hinged to the inner surface of the first part of the tail section and their rods are hinged to the inner surface of the head section. The cylinders of hydraulic jacks of the second group are hinged to the inner surface of the second part of the tail section and their rods are hinged to the inner surface of the first part of the tail section. The device preventing rotation of the tail section includes two groups of double-action hydraulic jacks positioned in the first and second parts of the tail section, each part accommodating one group of the hydraulic jacks. The cylinders of these hydraulic jacks are hinged to the inner surface of the tail section and their rods are hinged to plates. One end of each plate is hinged to the inner surface of the tail section, while its other free end passes through a hole in the tail section to come into contact with rock. A provision is made for a rock discharge mechanism, which is in fact blades positioned radially about the geometric axis of the cylindrical shell and rigidly fixed to the cutting tool of the head section. The rock discharge mechanism is also provided with haulage facilities of any known type, say, cars.
During operation fluid is fed to the head ends of the hydraulic jack cylinders of the device preventing the tail section from rotating. The rods of these hydraulic jacks are hence brought forward to move the plates. The free ends of the plates pass through the holes in the tail section to come into contact with rock, thus ensuring that the tail section is firmly fixed in rock. Then the fluid is fed to the head ends of the hydraulic jack cylinders of the traversing mechanism for turning the head section relative to the first part of the tail section. As a result, the rods of these hydraulic jacks are brought forward, thereby turning the head section relative to the tail section. At the same time the head section moves along the axis of the cylindrical shell due to the helical surface provided on the outer portion of the head section. With the head section turning and moving axially at the same time, the cutting tool performs effective operation in rock. Disintegrated rock is picked up by the blades in the lower part of the head section and loaded into a haulage facility, such as a car inside the head section in its upper part. Then the fluid is fed to the rod ends of the first group of the hydraulic jack cylinders of the device preventing rotation of the tail section in rock. As a result, the first part of the tail section firmly fixed in rock gets free. At the same time the fluid is fed to the head ends of the hydraulic jack cylinders of the traversing mechanism for turning the first part of the tail section relative to its second part. The rods of these cylinders are hence brought forward and turn the first part of the tail section relative to its second part. At the same time the first part of the tail section moves along the axis of the cylindrical shell until it comes into contact with the head section of the unit. This movement is made possible due to the helical surface provided on the outer portion of the tail section.
With the first part of the tail section fixed in rock getting free and moving, the cutting tool performs no operation in rock since the head section is stationary at this point and these operations are, therefore, auxiliary. Then the second part of the tail section fixed in rock gets free and the first part of the tail section becomes fixed in rock, after which the second part of the tail section turns and moves axially until it comes into contact with its first part. The cutting tool performs no operation for the same reason in the process and consequently these operations are also auxiliary.
The shield unit of this type features low efficiency, which stems from the fact that its operating cycle involves alternating effective and auxiliary operations, the period of time required for auxiliary operations being several times longer than that required for effective operations. Besides, the unit of such a design features a hydraulic system comprising four groups of hydraulic jacks which is fairly difficult to handle and repair. It is only one group of hydraulic jacks, namely those of the traversing mechanism that is directly involved in performing effective operation in rock. The other three groups of hydraulic jacks are designed for auxiliary operations. Since the blades are rigidly fixed to the cutting tool in the head section and turn together with the latter, rock, being too loose, is not fully discharged out of the head section. It accumulates therein and hence increases both the weight of the head section and the expenditure of energy required to move it. Thus, the unit should be periodically stopped to remove accumulated rock from the head section either with some known mechanisms or manually. This effects efficiency of the unit. What is more, disintegrated rock is loaded into haulage facilities only with the unit shut down, i.e. rock disintegration and loading into haulage facilities cannot be combined, which also decreases efficiency of the unit.